One problem which arises with flexible drives, particularly helically wound wire shafts of a type commonly used in a wide variety of tools and apparatus, is the tendency of the flexible drive shaft to curl up on itself under overload conditions, for example when the rotary head of a drilling or cutting tool encounters an obstruction. In the case of hands tools, this tendency of the flexible drive to coil up on itself when an overload occurs can result in danger to the operator.
Currently, when the cutting head meets an obstruction the operator has to disconnect the power source, free the cutting head from the obstruction and then reconnect the power source to the drive.
The present invention seeks to overcome this problem and makes use of the tendency of a wire wound flexible drive shaft to coil up on itself under overload conditions, thereby shortening the overall length of the shaft, to effect a temporary disconnection between the shaft and the driven, or driving member.